The removal of offshore structures often required the use of cold cutting technique such as diamond cable sawing and abrasive jet cutting (AJW), developed by Stolt Comex Seaway.

These technique present the following advantages, they are safe for personnel since they are either diverless or remotely operated, environmentally safe (causing no pollution or destruction of marine life), technically attractive (clean cut, reversible action, allowing the possibility of multiple shots, and usable in an explosive environment), and they are also cost-efficient, the cut is fully controlled until completion, there are minimum limitations on materials or thickness and the structure integrity remains unchanged.

The diamond cable sawing machines developed by Stolt Comex Seaway feature a specially designed diamond cable driven in rotation and pushed against the structure to be severed either horizontally or vertically. They are designed for external cutting of very large wall thickness material such as sandwich material (steel/concrete/steel), reinforced concrete or even pure stecl structures. This equipment was successfully used on various offshore projects including ZEEPIPE, EUROPIPE and DJENO.

The Abrasive Water Jetting (AWJ) technique used by Stolt Comex Seaway is based on the DIAJET equipment which produces on the surface a premixed slurry delivered to a cutting nozzle through a single hose. Cuts can be performed either externally (eg on pipeline) with an External Abrasive Jet Cutter (E-JAC), or from the inside (of piles, casing, etc), with an Internal Cutter(I-JAC) or with any type of deployment tool designed for a specific application (linear track, etc). this technique allows cuts to be made on large steel wall thickness (up to 140mm) and on some sandwich materials (depending on their thickness). This equipment was successfully used by Stolt Comex Seaway on several offshore projects including decommissioning on Hamilton Forbes platform and removal of the Shell Fulmar SALM Buoy.

This content is only available via PDF.
You can access this article if you purchase or spend a download.